The present invention relates to novel acrylates and methacrylates, to photosensitive compositions containing these compounds and to a process for the preparation of three-dimensional objects from said photosensitive compositons.
Radiation-sensitive liquid resins or resin systems can be used for a variety of utilities, typically as coating compositions, adhesives or photoresists. Quite generally, liquid resins or resin systems should also be suitable for fabricating three-dimensional objects by the stereolithographic technique described in U.S. Pat. No. 4,575,330; but many resins prove to be too viscous, whereas others are insufficiently light sensitve or suffer too severe shrinkage during the cure. The strength properties of the moulded articles or objects made from photocured resins are also often unsatisfactory.
Liquid resin systems for stereolithography comprising different mono- and diacrylates and mono- and dimethacrylates as well as a urethane acrylate or methacrylate and a monomeric or oligomeric diacrylate or methacrylate derived from bisphenol A or bisphenol F are disclosed in EP-A 425 441. When precured with laser light, these systems give green stages of superior green strength and, after the full cure, rigid-elastic objects whose flexibility is, however, insufficient for certain utilities.
EP-A 506 616 discloses liquid resin compositions of several acrylates and/or methacrylates which contain further hydroxyl group containing aliphatic or cycloaliphatic acrylates and/or methacrylates. The cured moulded articles made from these compositions by stereolithography have superior flexibility and tear propagation strength. A drawback of these compositions for processing in mechanical apparatus, however, is their rather high viscosity.
It has now been found possible to prepare novel hydroxyl group containing acrylates and methacrylates which, in conjunction with other acrylates or methacrylates, form low viscosity photocurable compositions which, when fully cured, give moulded articles of excellent flexibility.
Accordingly, the invention relates to compounds of formulae (Ia) and (Ib) 
wherein the substituents R1 are each independently of the other hydrogen or methyl, R2 is an unsubstituted C1-C20alkyl group or a C1-C20alkyl group which is substituted by one or more than one substituent selected from the group consisting of hydroxy, C6-C14aryl and halogen, an unsubstituted phenyl group or a phenyl group which is substituted by one or more than one substituent selected from the group consisting of C1-C6alkyl, hydroxy or halogen, or is a radical of formula xe2x80x94CH2-OR3, wherein R3 is an unsubstituted C1-C20alkyl group or a C1-C20alkyl group which is substituted by one or more than one substituent selected from the group consisting of hydroxy, C6-C14aryl and halogen, an unsubstituted phenyl group or a phenyl group which is substituted by one or more than one substituent selected from the group consisting of C1-C6alkyl, hydroxy and halogen, or is a C2-C6alkenyl group, a C2-C20acyl group or an unsubstituted cyclohexylcarbonyl group or a cyclohexylcarbonyl group which is substituted by one or more than one substituent selected from the group consisting of C1-C6alkyl, hydroxy and halogen, Z is a group of formulae (Ia)-(IIe) 
wherein Y is a direct bond, C1-C6alkylene, xe2x80x94Sxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94SOxe2x80x94, xe2x80x94SO2xe2x80x94 or xe2x80x94COxe2x80x94, and R1 is hydrogen or methyl, and wherein the aromatic and cycloaliphatic rings of formulae (IIa)-(IIe) are unsubstituted or substituted by one or more than one substituent selected from the group consisting of C1-C6alkyl, chloro and bromo.
R2 or R3 as C1-C20alkyl may be branched or, preferably, straight-chain alkyl. Typical examples of such alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, neo-pentyl, n-hexyl, octyl, decyl, dodecyl and icosyl.
The alkyl groups may also be substituted by one or more than one substituent selected from the group consisting of hydroxy, C6-C14aryl and halogen. Typical examples of substituted alkyl groups are hydroxymethyl, 2-hydroxyethyl, 2-hydroxypropyl, 2-chloropropyl, 2,3-dichlorobutyl, 2-phenylethyl and 2,3-diphenylbutyl.
R3 as C2-C6alkenyl may be branched or, preferably, straight-chain alkenyl. Typical examples of alkenyl groups are vinyl, prop-1-enyl, prop-2-enyl, 2-methylprop-2-enyl, n-but-3-enyl, n-pent-4-enyl and n-hex-5-enyl. Alkenyl groups containing two or three catbon atoms are preferred, and vinyl prop-1-enyl and prop-2-enyl are especially preferred.
Typical examples of C2-C20acyl groups are acetyl, propionyl, n-butyryl, isobutyryl, pivaloyl, hexyloyl, octyloyl, tetradecyloyl, hexadecyloyl and octadecyloyl.
R3 as phenyl or cyclohexylcarbonyl may be unsubstituted or substituted by one or more than one substituent selected from the group consisting of C1-C6alkyl, hydroxy and halogen. Typical examples of such groups are tolyl, xylyl, mesityl, 2-hydroxyphenyl, 4-hydroxyphenyl, 2-chlorophenyl, 4-chlorophenyl, 3,5-dichlorophenyl, 2,4-dichlorophenyl, 2,6-dimethylcyclohexylcarbonyl, 4-hydroxycyclohexylcarbonyl, p-hydroxybenzyl, p-chlorobenzyl and o-ethylbenzyl.
The aromatic and cycloaliphatic rings in formulae (IIa)-(IIe) are preferably unsubstituted
In the compounds of formulae (Ia) and (Ib) R2 is preferably C1-C20alkyl, phenyl, C1-C20alkoxymethyl, phenoxymethyl or cyclohexycarbonloxymethyl.
Especially preferred compounds of formulae (Ia) and (Ib) are those wherein R2 is n-butyl, phenyl, n-butoxymethyl, phenoxymethyl or cyclohexylcarbonyloxymethyl.
The most preferred meaning of R2 is n-butoxymethyl.
Z in formulae (Ia) and (Ib) is preferably a group of formula (IIc) or (IIe).
Compounds of formulae (Ia) and (Ib) are especally preferred wherein Z is 
The compounds of formulae (Ia) and (Ib) can be prepared by per se known processes. A further object of the invention is a process for the preparation of compounds of formulae (Ia) and (Ib), which comprises reacting a diglycidyl ether of formula (III) 
wherein R2 and Z have the above meanings, in a manner known per se, with acrylic or methacrylic acid.
The diglycidyl compounds of formula (III) are known and disclosed, inter alia, in EP-A 22 073.
The reaction of the diglycidyl compounds of formula (III) with acrylic or methacrylic acid normally gives a mixture of compounds (Ia) and (Ib), compound (Ia) being the main product and compound (Ib) being obtained in comparatively minor amounts (c. 10-20%). Separation of the two structurally isomeric compounds for use in photosensitive compositions is not necessary.
Illustratative specific examples of the diglycidyl compounds of formula (III) are:
2,2-bis[p-(3-butoxy-2-glycidyloxypropoxy)phenyl]propane,
2,2-bis[p-(3-methoxy-2-glycidyloxypropoxy)phenyl]propane,
2,2-bis[p-(3-ethoxy-2-glycidyloxypropoxy)phenyl]propane,
2,2-bis[p-(3-dodecyloxy-2-glycidyloxypropoxy)phenyl]propane,
2,2-bis[p-(3-tetradecyloxy-2-glycidyloxypropoxy)phenyl]propane,
2,2-bis[p-(3-benzyloxy-2-glycidyloxypropoxy)phenyl]propane,
bis[p-(3-butoxy-2-glycidyloxypropoxy)phenyl]methane,
1,3-bis[p-(3-phenoxy-2-glycidyloxypropoxy]benzene,
bis[p-(3-butoxy-2-glycidyloxypropoxy)phenyl]sulfone,
2,2-bis[p-(3-cyclohexoxy-2-glycidyloxypropoxy)phenyl]propane,
2,2-bis[4-(3-butoxy-2-glycidyloxypropoxy)-3,5-dibromophenyl]propane,
2,2-bis[p-(3-allyloxy-2-glycidyloxypropoxy)phenyl]propane,
2,2-bis[p-(3-phenoxy-2-glycidyloxypropoxy)phenyl]propane,
2,2-bis[4-(3-butoxy-2-glycidyloxypropoxy)cyclohexyl]propane,
2,2-bis[p-(3-cyclohexylcarbonyloxy-2-glycidyloxypropoxy)phenyl]propane,
2,2-bis[p-(2-glycidyloxyhexoxy)phenyl]propane, and
2,2-bis[p-(2-phenyl-2-glycidyloxyethoxy)phenyl]propane.
A further object of the invention is a photosensitive composition comprising
(a) 5-65% by weight of a compound of formula (Ia) or (Ib) according to claim 1,
(b) 15-70% by weight of one or more than one bifunctional acrylate or methacrylate having a molecular weight in the range from 150 to 450 and differing from compound of formula (Ia) or (Ib),
(c) 0-40% by weight of one or more than one monomeric polyfunctional acrylate or methacrylate having a functionality of not less than 3 and a molecular weight of not more than 600,
(d) 0-10% by weight of at least one monofunctional acrylate or methacrylate,
(e) 0-10% by weight of N-vinylpyrrolidone or N-vinylcaprolactam,
(f) 2-10% by weight of at least one photoinitiator, and
(g) 0-60% by weight of at least one urethane acrylate or methacrylate having a functionality of 2-4 and a molecular weight in the range from 500-10000, such that the sum of the amounts of components (a) to (g) together is 100% by weight.
Compounds useful as component (b) include the diacrylate and dimethacrylate esters of aliphatic, cycloaliphatic or aromatic diols, including 1,3- or 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, tripropylene glycol, ethoxylated or propoxylated neopentyl glycol, 1,4-dihydroxymethylcyclohexane, 2,2-bis(4-hydroxycyclohexyl)propane, bis(4-hydroxycyclohexyl)methane, hydroquinone, 4,4xe2x80x2-dihydroxybiphenyl, bisphenol A, bisphenol F, bisphenol S, ethoxylated or propoxylated bisphenol A, ethoxylated or propoxylated bisphenol F or ethoxylated or propoxylated bisphenol S.
Such diacrylates and dimethacrylates are known and some are commercially available, typically those sold by the SARTOMER Company under the product names SR 348 for the dimethacrylate of ethoxylated bisphenol A, SR 349 for the diacrylate of ethoxylated bisphenol A, SR 247 for neopentyl glycol diacrylate and SR 344 for polyethylene glycol 400 diacrylate.
It is preferred to use a diacrylate or dimethacrylate of ethoxylated bisphenol A as component (b).
Compounds useful as component (c) are typically triacrylates or trimethacrylates of formula (IV) or (V)
R4xe2x80x94CH2xe2x80x94Cxe2x80x94(CH2xe2x80x94R5)3xe2x80x83xe2x80x83(IV),
R5xe2x80x94CHxe2x80x94(CH2xe2x80x94R5)2xe2x80x83xe2x80x83(V),
wherein R4 is hydrogen, methyl or hydroxyl, and R5 is a radical of formula (VI) 
wherein n is 0 or a number from 1-3 and R6 and R7 are each independently of the other hydrogen or methyl.
Among the compounds of formulae (IV) and (V), those compounds of formula (IV) are especially preferred in which R4 is methyl and R5 is a radical of formula (VI), wherein n is 0.
Illustrative examples of compounds which may be used as component (c) are:
1,1,1-trimethylolpropane triacrylate or methacrylate, ethoxylated or propoxylated 1,1,1-trimethylolpropanetriacrylate or methacrylate, ethoxylated or propoxylated glycerol triacrylate, pentaerythritol monohydroxy triacrylate or methacrylate; and also higher functional acrylates or methacrylates such as dipentaerythritol monohydroxy pentaacrylate or bis(trimethylolpropane) tetraacrylate. Such compounds are known to the skilled person and some are commercially available.
Preferably the compounds useful as component (c) have a molecular weight in the range from 250 to 700.
It is especially preferred to use trimethylolpropanetriacrylate and trimethylolpropane trimethacrylate as component (c).
Component (d) of the novel compositions may be selected from the following compounds:
allyl acrylate, allyl methacrylate, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate and n-dodecyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2- and 3-hydroxypropyl (meth)acrylate,
2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate and 2- or 3-ethoxypropyl (meth)acrylate, tetrahydrofurfurylmethacrylate, 2-(2-ethoxyethoxy)ethylacrylate,
cyclohexyl methacrylate, 2-phenoxyethyl acrylate, glycidyl acrylate and isodecyl acrylate. Such products are also known and some are commercially available, as from SARTOMER.
2-Phenoxyethylacrylate is especially preferred
The novel compositions may contain up to 10% by weight of N-vinylpyrrolidone or N-vinylcaprolactam or a mixture thereof as component (e). It is preferred to use N-vinylpyrrolidone.
Any type of photoinitiator which, when irradiated suitably, forms free radicals can be employed as component (f) in the novel compositions. Typical known photoinitiators are benzoins, benzoin ethers, including benzoin, benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether, benzoin phenyl ether and benzoin acetate; acetophenones, including acetophenone, 2,2-dimethoxyacetophenone and 1,1-dichloroacetophenone; benzil, benzil ketals such as benzil dimethyl ketal and benzil diethyl ketal; anthraquinones, including 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone and 2-amylanthraquinone; triphenylphosphine; benzoylphosphine oxides, for example 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Luzirin TPO); benzophenones such as benzophenone and 4,4xe2x80x2-bis(N,Nxe2x80x2-dimethylamino)benzophenone; thioxanthones and xanthones; acridine derivatives; phenazine derivatives; quinoxaline derivatives or 1-phenyl-1,2-propanedione; 2-O-benzoyl oxime; 1-aminophenyl ketones or 1-hydroxyphenyl ketones such as 1-hydroxycyclohexyl phenyl ketone, phenyl 1-hydroxyisopropyl ketone and 4-isopropylphenyl 1-hydroxyisopropyl ketone.
Suitable initiators are also are electron transfer initiators of the xanthone type, for example 2,4,5,7-tetraiodo-6-hydroxy-9-cyano-3H-xanthen-3-one which, together with suitable electron donors, have a high reactivity in the visible range of the spectrum.
Another class of suitable photoinitiators (f) comprises the ionic dye-counter ion compounds which are capable of absorbing actinic radiation and generating free radicals which initiate the polymerisation of the acrylates (a) to (d) and optionally (g). The compositions of the invention containing ionic dye-counter ion compounds can be cured more variably in this way with visible light within the adjustable wavelength range of 400-700 nm. Ionic dye-counter ion compounds and their mode of action are known, for example from EP-A-0 223 587 and U.S. Pat. Nos. 4,751,102; 4,772,530 and 4,772,541. Typical examples of suitable ionic dye-counter ion compounds are the anionic dye-iodonium ion complexes, the anionic dye-pyrylium ion complexes and, especially, the cationic dye-borate anion compounds of formula 
wherein X+ is a cationic dye and R8, R9, R10 and R11 are each independently of one another an alkyl, aryl, alkaryl, allyl, aralkyl, alkenyl or alkynyl group, or an alicyclic or saturated or unsaturated heterocyclic group.
Particularly suitable photoinitiators which are normally used in conjunction with a HeCd laser as souce of irradiation are acetophenones such as 2,2-dialkoxybenzophenones, and xcex1-hydroxyphenylketones, typically 1-hydroxycyclohexylphenyl ketone or (2-hydroxyisopropyl)phenyl ketone (=2-hydroxy-2,2-dimethylacetophenone).
A particularly preferred photoinitiator is 1-hydroxycyclohexylphenyl ketone.
The novel compositions may also contain other photoinitiators of different sensitivity to radiation of emission lines of different wavelengths. The inclusion of such photoinitiators effects the better utilisation of a UV/VIS light source which radiates emission lines of different wavelength. It is advantageous to choose these other photoinitiators and to use them in such a concentration that a uniform optical absorption is produced with respect to the emission lines used.
The urethane acrylates used in the novel compositions as component (g) are known to those skilled in the art and can be prepared in known manner, typically by reacting a hydroxyl-terminated polyurethane with acrylic acid or methacrylic acid to the corresponding urethane acrylate, or by reacting an isocyanate-terminated prepolymer with hydroxyalkyl acrylates or methacrylates to the urethane acrylate. Suitable processes are disclosed, inter alia, in EP-A 114 982 and EP-A 133 908. The molecular weight of such acrylates is generally in the range from 400 to 10000, preferably from 500 to 7000. Urethane acrylates are also commercially available and are sold by UCB under the registered trademark EBECRYL(copyright), by Morton Thiokol under the registered trademark Uvithane(copyright)or by the SARTOMER Company under the product names SR 9504, SR 9600, SR 9610, SR 9620, SR 9630, SR 9640 and SR 9650.
It is preferred to use those urethane acrylates with have a molecular weight from 500-7000 and which are prepared preferably from aliphatic educts.
The novel photosensitive compositions can be polymerised by irradiation with actinic light, typically with electron beams, X-rays, UV or VIS light, i.e. with radiation in the wavelength range from 280-650 nm. Particularly suitable light sources are HeCd, argon or nitrogen laser light as well as metal vapour and NdYAG lasers with multiple frequency. Those skilled in the art will know that the appropriate photoinitiator for each selected light source must be chosen and, if necessary, sensitised. It has been found that the depth of penetration of the radiation into the polymerised composition and the processing rate are directly related to the absorption coefficient and the concentration of the photoinitiator. In stereolithography it is preferred to use those photoinitiators which generate the highest number of resulting free radicals and make possible the greatest depth of penentration into the compositions to be polymerised.
The invention further relates to a process for the production of three-dimensional objects from the novel liquid compositions by lithographic methods, especially by stereolithography, in which a layer of novel liquid composition is irradiated over the entire surface or in a predetermined pattern with a UV/VIS light source, such that within the irradiated areas a layer solidifies in a desired layer thickness, then a new layer of novel composition is formed on the solidified layer, which is likewise irradiated over the entire surface or in a predetermined pattern, and such that three-dimensional objects are formed from a plurality of solidified layers which adhere to one another by repeated coating and irradiation.
In this process it is preferred to use a laser light which is preferably computer-controlled.
The novel compositions are distinguished by low viscosity and hence good processing properties. The green models obtained by precuring with laser light and the fully cured objects have good mechanical properties, especially superior flexibility.
The novel compositions can be used typically as adhesive or coating compositions or as formulations for stereolithography or other methods of model construction with photopoplymers.
If the novel compositions are used as coating compositions, clear and hard coats are obtained on wood, paper, metal, ceramic or other surfaces. The coating thickness can vary over a very wide range and be from c. 1 xcexcm to c. 1 mm. Relief images for printed circuit boards or printing plates can be produced from the novel compositions, conveniently by computer-controlled laser light of appropriate wavelength or using a photomask and a suitable light source.
It is preferred to use the novel compositions for the production of photopolymerised layers, especially in the form of three-dimensional objects which are formed from a plurality of solidified layers which adhere to one another.